It is also a huge deal because since (at least in France) the government forced ISPs to log DNS queries, a lot of browsers (and latest android and iOSversion’s) have now migrated to DNS over https or TLS DNS, which means that the only clear text DNS query they can intercept is the one to fetch your secure DNS service address. Now, having a trusted CA installed in browsers means that they can also spoof the identity of this secure name service, and regain a bit of control.

They invested a lot in surveillance technology (for both good and bad reasons), and https, DNS and encrypted messaging / phone calls means this was all for nothing.

And yes, by being authorized as a trusted CA, you can effectively spoof pretty much anything by setting a proxy. Some tools even leverage this for app analysis. Look up mitmproxy for example, or squid. A lot of companies already do this to inspect inbound / outbound traffic.